Saturn



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A view of Saturn, from behind. The sun can be seen on the horizon.


Quick Facts
  • One Saturn year is about 29.5 Earth years, but its day is only 10 hours and 39 minutes.
  • Saturn is actually a very light planet; so much, in fact, that if one were to find a large enough pool of water and drop Saturn in it, it would float.
  • Saturn gives off about 2.5 times as much heat as it receives from the sun daily.
  • Saturn has 7 rings, (lettered A to F, and can be 180,000 miles across, but are so thin (660-9800 feet wide), the naked eye cannot perceive them.
  • Saturn's rings were first discovered in the 1600s by Galileo Galilei, but were not classified as "rings" until Christiaan Huygen's discovery in 1656.
  • Saturn's largest moon, Titan, is 3201 miles in diameter, but some smaller moons can be even less than six miles in diameter.
  • The moons of Saturn were given classical names, such as Phoebe and Calypso, until 2000 when the Inuit moons (Siarnaq, Ijiraq, &c.) were discovered. In 2005, Scandinavian astronomers named new moons Skoll, Ymir, &c. Now, any new moons are given a scientific name such as S/2007 S 2 and S/2004 S 13.
  • Titan's atmosphere consists chiefly of nitrogen, and if it had water and higher temperatures, could support life.
  • Saturn's rings orbit the planet at varying tilts, anywhere from 30-80* at any point in time in the year.
  • It is believed that 50 million years in the future, Saturn's rings will disappear.

The Nine Planets


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A foreshortened view of the nine planets, Earth's moon, a comet, and a few asteroids.


Planets are celestial bodies that orbit the sun or another star and shine by the light they reflect. Another common definition is a piece of rock and metal somewhere in the universe that is big enough to be come spherical due to its field of gravity, and may or may not have one or more smaller satellites, or moons, orbiting them. In the Milky Way solar system, located on Orion's Arm, there are eight major planets and one dwarf planet as well as thousands of minor planets. These planets, in order, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and the dwarf planet, Pluto. Some of the minor planets include Ceres, Pallas, Juno, and Vesta, located between Mars and Jupiter in the asteroid belt.


Saturn, the Planet



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A view of Saturn taken from the Hubble Space Telescope. Here, the shadow Saturn makes due to the sun's rays can be seen on its rings.


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B Ring spokes in a low-phase-angle Cassini image of Saturn's rings.
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The Greek god, Chronos, eating one of his children.

Saturn, named for the Roman equivalent of Chronos (the father of Zeus and the Titans), is the sixth major planet and the second largest in the Milky Way solar system. Unlike Earth, it has at least 60 moons, the three largest being Titan (5150 km diameter at equator), Rhea (1530 km diameter at equator), and Iapetus (1460 km at diameter). Only 34 of Saturn's discovered moons are named, and of all the moons whose rotations are known, all but Phoebe and Hyperion have synchronous rotation (rotate at the same time that they revolve).

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A diagram of Saturn and its 34 named moons. The moons are both in relative size and distance to the planet. One inch is about 750,000 miles.

Saturn's equatorial diameter is 119,300 km (74,130 mi), which is about 9.4 times as large as
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A size comparison of Saturn, to Earth.
Earth. Its mass is 5.69 x 10^26 kg, which is 95 times as massive as Earth. However, Saturn's gravity is only 1.08 times as much as Earth's, and its composition is so light that it is actually 30% less dense than water. In other words, if Saturn were dropped in a large enough area of water, it would float. Due to Saturn's fast rotation (10 hour, 39 minute days), its poles are visibly flattened, giving it a slightly pressed in appearance. A fast rotation means fast winds. Wind blowing at Saturn's equator can reach 1100mph, and blows mostly easterly.

Saturn's atmospheric banding (the distinct difference in yellow shades on the planet's surface) is very similar to Jupiter's. Its atmosphere itself is composed mostly of hydrogen with small amounts of helium and methane. This suggests that if Saturn were not so cold (average temperature of 88K, -185*C, or -290*F), and had a higher density, it could support life. However, this is not possible to its distance from the sun, 9.539 AU, 9 times as far away from the sun as Earth is.


Saturn's Rings


Saturn is usually identified by its many rings, made of small, orbiting planetoids, including a few larger "shepherd moons" which guide the smaller pieces of ice and rock around Saturn in their orbits. The formation of Saturn's rings are unknown, but a theory is a massive collision with a planet and the dust particles remaining began to orbit. Saturn's rings are separated into seven divisions: rings A through G. These rings are not named by the order they come in, but the order they were discovered. This means, that from the center outward, the rings are named D, C, B, A, F, G E.

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The original sketch of Saturn's rings viewed at different times of the year, drawn by Christiaan Huygens.

Saturn's A and B rings are divided by the Cassini Division (an enormous gap between Saturn's rings, visible in most photographs of Saturn), discovered by Giovanni Cassini in 1675. The A and F rings are divided by the Roche Division, named for Édouard Roche, the man who discovered the Roche Limit (the distance in which a celestial body, held together only by its own gravity, will disintegrate due to a second celestial body's tidal forces exceeding the first body's gravitational self-attraction). There are other divisions in the rings, but they are not as well known, and some are named merely as placeholders to divide each of the rings, such as the Encke Disvision which splits the A ring.

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A more scientific diagram of Saturn's rings, the placement of closer moons, and the difference in the divisions. Here, all seven divisions can be seen.

Web Links
www.pds.jpl.nasa.gov/planets/choices/saturn1.htm
www.windows.ucar.edu/tour/link=/saturn/saturn.html
www.enchantedlearning.com/subjects/astronomy/planets/saturn
NASA



ReferencesThe World Book Encyclopedia. "Saturn." Chicago: World Book, Inc., 2006. pp.151-53.
Illingworth, Valerie, ed. The Facts On File Dictionary of Astronomy. New York: Laurence Urdary Associates, 1985. pp. 283, 333-35.
"Saturn." Calvin J. Hamilton. Solar Views. www.solarviews.com/eng/saturn.htm.
"World Book at NASA: Saturn." Brian Dunbar, ed. NASA. www.nasa.gov/worldbook/Saturn.worldbook.html .